Formylation is an important process in organic chemistry. The versatile chemical properties of formylated compounds and their usefulness in a variety of applications as end products and as intermediates, makes them a significant family of compounds. Accordingly, researchers have devoted a great deal of effort over the years to the development of effective formylation technology.
One of the earliest reported methodologies for the formylation of an aromatic compound is the well known Gattermann-Koch reaction, first described in 1897. In accordance with this reaction scheme, benzene and alkylbenzenes are reacted with carbon monoxide and hydrogen chloride in the presence of ammonium chloride at high pressure to produce formylated compounds. Addition of cuprous chloride allows the reaction to proceed at atmospheric pressure.
Hamilton et al., U.S. Pat. No. 3,369,048, seeking to improve on the Gattermann-Koch reaction, disclose a variation wherein crystalline aluminosilicate catalysts are employed in the reaction in lieu of aluminum chloride and cuprous chloride.
Renner, U.S. Pat. No. 4,195,040, provides still another variation of the Gatterman-Koch process wherein carbon monoxide, hydrogen chloride and an aluminum chloride catalyst are employed in the presence of a chlorobenzene solvent.
Rahm et al. Synthetic Communications, Vol. 12, No. 6, pp. 485-487 (1982) describes a process wherein aromatic compounds are formylated using acetone cyanohydrin and aluminum chloride.
Martinez et al., J. Chem. Soc. Chem. Commun., pp. 1571-1572 (1990) provides a process for the formylation of less active aromatic compounds using a trifluoromethanesulphonic anhydride/dimethylformamide complex.
However, many of these, and other, prior art processes for the formylation of aromatic compounds suffer from disadvantages which make them commercially problematic and/or impractical. Indeed, many of the aromatic formylation methods developed to date employ difficult reaction schemes, require expensive equipment, necessitate the use of costly and/or hazardous reagents, and/or are applicable to only a select number of aromatic compounds.
New and/or better processes for the formylation of aromatic compounds are needed. The present invention meets this need by seeking to address many of the drawbacks of prior art processes. The present invention provides a new and surprisingly effective process which is useful for the formylation of a wide variety of aromatic compounds. The present process employs a relatively simple and economically feasible methodology, and provides a practical solution to many of the problems of formylation technology to date.